Low-Pressure Molding: How an Overmolding Machine Can Help

Low-Pressure Molding and Overmolding

Low-pressure molding is vital for protecting sensitive electronic components against the environment, like moisture, dust and dirt. As an alternative to high-pressure molding, it allows for overmolding on more sensitive equipment. While one may assume a low-pressure method could take more time than a high-pressure one — low-pressure molding machines can seal sensitive electronics and have them ready to handle in seconds

What injection molding does:

Injection molding is used to manufacture parts in a large volume and is typically used where the same part is being produced many times in succession. As far as assembly goes, injection molding is cost-effective, especially when used in mass production. This process is commonly used to create a wide variety of products and parts, ranging from containers to automotive body parts. Injection molding is a complex process, reliant on several steps and moving parts but with three main components. According to Milacron, these are the feed hopper, the screw and the heated barrel. Plastic is placed in the hopper, typically in granular or powder form, and then fed into the heated barrel. The screw, along with heater bands, melt the materials using frictional action. The plastic, now melted, is injected through a nozzle into a mold. 

Injection molding is generally used to efficiently create plastic materials based on approved molds. This process allows for making intricate geometrical shapes due to the pressure exerted and can allow for using different types of plastic simultaneously. 

Double shot injection molding:

Double shot molding is used for complex plastic objects, consisting of multiple materials and various colors. This, as well as typical injection molding, is generally cost-effective and viable for mass-production. This manufacturing process creates complicated molded parts with two different materials by molding plastic around a metal or plastic insert. The process, broken down into two steps, is — the first material is injected into a mold that will make a piece of the product. This is followed up by a second injection, of a different but compatible material with the initial piece. The plastic resins form a molecular bond, creating a multi-resin product, says Midstate Mold. This method is recognized for lowering unit costs, reducing waste, and improving product quality. 

Running an overmolding project:

Beginning an overmolding project requires knowing what materials you wish to work with. You need a substrate — the first piece in what will become a singular product. It can be an electrical connector, a molded plastic part or metal. Then, you need the overmolding material, which is typically plastic and heated to a melting point. 

The process of overmolding, using a MoldMan molding machine, goes as follows:

  1. •Find your low-pressure molding materials (polyamides, polyamide acrylic hybrids, copolyesters).
  2. •Determine if you’re using a single or multi-cavity mold set. 
  3. •Monitor temperature and pressure using control screen
  4. •Place low-pressure molding materials into insulated upper-hopper
  5. •The material will come into contact with heat, before being injected into the cavity. This can allow for quick material changes.
  6. •The machine’s one-ton clamping force will aid in material distribution, even when using copolyesters

Overmolding is also used for a wide variety of products and purposes, from toothbrushes to electronics. Materials can also vary, but with that, compatibility needs to be taken into account. Typical applications of overmolding include: plastic over plastic, rubber over plastic, plastic over metal, and rubber over metal. It can be used as a way to combine parts without the use of fasteners or adhesives, as well. Overmolding, as a method of low pressure molding, is useful for working on a wide range of products in an efficient manner. Using an overmolding machine can allow you to produce a variety of products but with one piece of equipment. 

Compared to other tools of protecting electronics — like potting — overmolding is a faster, simpler process with less waste (leftover materials can be recycled into new materials or are biodegradable). Using an overmolding machine can be vital for protecting valuable electronics from heat, water, dust, and the general wear-and-tear of use. 

Contact us about electronic overmolding services and we will coordinate with our partners at Mold-Man Systems to provide the tools you need to ensure your electronic assemblies are protected against the strain of the environment.


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